Robust computational analysis methods for multiple-axis machining in CAD/CAM/CNC systems (Tool path generation)

The objective of this research is to improve the machining efficiency and accuracy of CAD/CAM/CNC systems in multi-axis tool path generation, machined surface error analysis, NC verification/simulation, and machine tool trajectory interpolation. To improve the machining efficiency, an optimal tool path generation method based on the machining potential field (MPF) of the part surface has been developed. The machining potential field represents the best cutting tendency on the part surface. An iterative searching algorithm has been developed for the optimal tool path generation. The tool paths are initialized from the part surface where possesses the largest machining strip widths. The adjacent tool paths are then propagated by maximizing the machining strip width and minimizing the overlapping of the machining strips. Hence, the total tool path length and the NC machining time are reduced. To minimize the positioning errors caused by the chordal deviation and the swept deviation in multi-axis NC machining, we develop a surface-based NURBS path interpolation method. By using the developed surface-based NURBS path trajectory interpolation, CNC control units can directly take the cutter contact (CC) paths as the reference points to generate the machine tool motions within the specified accuracy. To improve the machining accuracy, the actual cutting shapes of the milling cutters in multi-axis NC machining need to be analyzed. Swept envelope with G-buffer models has been developed in this research for machined surface error analysis. By analyzing the cutter geometry and tool motion in multi-axis NC machining, the governing functions of the cutter swept envelope with G-buffer models have been explicitly formulated. The swept envelope is determined by integrating the swept profiles along the multi-axis tool motion trajectory. The final machined surface can be determined by the conjugate geometry of the swept envelopes and the workpiece G-buffer models. Computer implementation, illustrative examples, and NC machining testing examples are also presented in this dissertation. The results show the developed machining potential field technique, the surface-based NURBS path interpolation, and the swept envelope with G-buffer models can significantly increase the machining efficiency and reduce the machining errors. The technique presented in this dissertation can be used to automate 5-axis tool path generation and to improve the machining efficiency and accuracy of CAD/CAM/CNC systems.